Unit ventilator



April `18, 1939. J. T. MIDYETTE, JR

UNIT VENTILATOR Filed Oct. 14, 1935 2 Sheets-Sheet l @Jer l f 4 o i, w,2,/ .md 2RM f f F Naar #l I .dT

y D5 ,M n J Y amounts of fresh air vary according to the re- UNITVENTILATOR Minneapolis Minn., a corporation of Delaware ApplicationOctober 14, 1935, Serial No. 44,899

10 Claims.

of the class described with control mechanisms responsive-to spacetemperature .and discharge temperature for positioning lthe damper andthe radiator valves.

Another object of this invention is to provide a control system for aunit ventilator that is placed in operation when the room temperaturereaches a predetermined value. V

In various parts of the country the heating and Ventilating codes callfor a predetermined minimum amount of fresh air to be delivered to afspace, and these predetermined minimum guirements of the variouslocalities. It is, therefore, an object of this invention to provide ameans for admitting a minimum amount of fresh air to the space withmeans for easily adjusting this minimum amount of fresh air whereby thevarious heating and Ventilating codes may be readily complied with.

Other objects and advantages will become apparent to those skilled inthe art upon reference to the accompanying specication, claims andrawings, in which drawings: Y

.Figure l is a perspective view system applied to a unit ventilator withportions thereof broken away for purposes of illustration.

Figure 2 isa schematic wiring diagram of one form Aof the control systemthat may be applied to the unit ventilator shown inA Figure l.

Figure 3'is a schematic wiring diagram of 'another -form of the controlsystem that may likewise be applied to the unit ventilator disclosedinliigure'l'. f l A Although my invention may be applied equally well toa plenary system, itis shown'as applied to .a unit ventilator generallydesignated at 10. The

,unit ventilator I comprisesfatfront wall ||V and rearwalls |2- and'.I3. The Arear walls |2'and '|3` are connected together byafhorizontally extending Wall I4. The top `of the ventilator I0 isclosed bya top wall I5, Yand"likewise-the bottom of the unit .Ventilatoris closedby a bottom wall or base,

[|6. Loc'ated'- within the. unit ventilator I0, is

of my control (ci. 23H8) vertically extending transverse partition I1which divides the unit ventilator into two chambers, one chamberenclosing the air conditioning elements, and the other chamber enclosingthe control elements.

Located in the front wall is a return air opening I8, and likewiselocated in the rear wall |3'is a fresh air opening I9. These openings I3and' I9 may be provided with suitable' grills, not shown. Locatedbetween the openings I3 and I3 is a vertically extending heme-20,.dividing the lower portion of the air conditioning chamber into a freshair chamber and 'a return air chamber. A damper 2| is suspended abovethe baille 20-by means of brackets 22 secured toshafts 23 so that whenthe damper 2| is moved into the position shown in Figure 1 the fresh airchamber is cut off, and when the damper 2| is moved to the right of theposition shown in Figure 1 the return air chamber is cut off. The damper2| is adapted to be positioned between either of these extreme positionsin a manner to be described fully hereafter.

Located above the damper 2| is a fan 24, having an outlet opening 25.Fan 24 is driven through a shaft 26 by means of an electric vmotor 2l.Located above the fan 24 are superimposed radiators 23 and 29. The-topwall\|5 is provided with a discharge opening 39 so that the fan 24 -maydraw either fresh air or return air, or a -mixture thereof, asdetermined .by the damper 2| over the radiators 28 and 29, to bedischarged into the space to be conditioned through the dischargeopening 3Il. Heating fluid such as steam may be-supplied to theradiators 28 and 29 by means of pipes 32 -and 33, respectively. The flowof heating uid through the pipe 32 is controlled by means of a valve 34,and likewise the flow of heating fluid through' the pipe 33-iscontrolled by a valve 35. The valves 34 and 35 are provided with valvestems 36 and 31; respectively, which are forced outwardly by means Aofcompression, springs 38 and 39, respectively. The springs 38 and 39 biasJ-'thevalves 34 and 35 to `an open position. The

valve stemsA 36. and 311 carry rollers 4I! and 4I,

which are adapted toY co-act with cams\42 and 43 locatedson a shaft 44.Cams 42 and 43 are adapted upon turning movement ofthe same toactagainst -the rollers`40 and 4| to move the 'valves 34 and- 35.towards a closed position.

" Also mounted.. on the shaft .f-:44 :is a cam 45 co-acting with aroller 46 mounted yon a lever 41, pivoted as at 43. Lever 4I.actsthrough `a link 49 A and a-crank 50 secured tothe damperfshaft 23 by aproportioning motor 55 in a manner to be described hereafter. The motor55 may take theY form of the motor disclosed in Patent No.2,032,658`issued to W. H. Gille on March 3, 1936 or disclosed inapplication Serial No. 673,236 filed 'by Lewis L. Cunningham on May 27,1933.

Located in the space to 'be conditioned is a thermostat 56 preferably ofthe potentiometer type shown and described in patent No. 2,041,050

issued to Lewis L. Cunningham.

Located in thecontrol chamber of unit ventilator |0 `is a controller 51,preferably of the potentiometertype. The controller 51 is connected bymeans of a capillary tube 58 to a bulb 59 located in the dischargeopening 30 of the unit Ventilator I0, so that the controller 51 isoperated in response to changes in temperature of the discharge air fromthe unit ventilator. The controller 51 may take the form also shown inLewis L. Cunningham Patent No. 2,041,050.

Also located within the control chamber is a variable resistance 60operated by a knob 6|.

Located in the return air opening I8 is a thermostat 62 which may be ofthe typev shown in Patent No. 1,676,921, issued to L. A. M. Phelan etal., on July 10, 1928.

The space temperature controller 56; the discharge temperaturecontroller 51, the variable resistance 60, the return air temperaturecon troller 62 and the proportioning motor 55 are suitably connectedtogether by means of conduits 63.

The manner in which these various control elements are associated andthe manner in which they form the control function for the unit venti'-lator may be obtained by reference to Figure 2 of the drawings. InFigure 2 of the drawings I have shown the motor 55 to be of the typedisclosed in the Willis H. Gille Patent No. 2,032,658. A lost motionconnection of limited amount is shown to exist between the motor crank53 and the associated link 52, this lost motion being accomplished bymeans of a slot 65 in the link 52 cooperating with a pin 66 carried bythe crank 53. A spring 61 normally urges the link 52 upwardly and,consequently, urges the crank 53 in a clock-wise direction. However,when the link 52 is moved to its extreme upward position, which positioncorresponds to the position shown in Figure l, the crank 53 is allowedto move in a clockwise direction a limited amount by reason of the lostmotion connection for reasons to appear more fully hereafter.

' The shaft 54 is operated through bevel gears 68' and 69 by means of arotary shaft 10. The rotary shaft 10 carries a gear 1| which is rotatedthrough a reduction gear train 12 by a motor rotor 13. The motorrotor 13is operated by field windings 14, 15 and 16. The eld winding 14 performsa holding function and isv of sufficient strength to act against thespring 61- to maintain the shaft 10 in any given position but notsufiicient to move the shaft. The field winding -18 is an operatingwinding butis not sumciently strong in itself to-cause operation of theshaft'l! against the tension of the spring 81.

x knob 6| is shown to comprise three resistances 92,

However, when both windings 14 and 16 are energized simultaneously thevshaft 10 is rotated against the tension of the spring 61 to move thedamper 2| from a fresh air restricting or closed position. opposition tothe eld winding 14 so that when the eld windings 14 and 15 areenergized, the maintaining or holding action of the field winding 14 isneutralized and the shaft 10 is allowed to be rotated by means of the`spring 61 to move the damper 2| towards a fresh air restrictingposition as shown in Figure 1.

The shaft 18` also carries a bevel gear 11 engaging the bevel gear 18 tooperate an abutment member 19. The abutment member 19 carries a slideradapted to slide across a potentiometer coil 8|. The abutment member 19also carries fingers 82 and 83. The finger 82 co-acts with a limitswitch comprising contacts 84 and 85 and in a like manner the contactfinger 83 co-acts with a limit switch comprising contacts 86 and 81.When the damper 2| is moved to an extreme closed or fresh airrestricting position the contact finger 82 breaks contact between thecontacts 84 and 85 and when the draft damper 2| is moved to an extremeopen or return air restricting'position the finger 83 breaks contactbetween the contacts 86 and 81. v

For purposes of illustration, the space temperature controller 56 isshown to comprise a slider 88 adapted to slide across a potentiometercoiI 89 and the discharge temperature controller 51 is shown to comprisea slider 90 adapted to slide across a potentiometer coil 9|. Uponincreases in temperature the sliders 88 and 90 are moved to the right,and upon decreases in temperature the sliders 88 and 90 are moved to theleft as shown by the characters H and C, respectively.

The variable resistance 60 operated by the 93 and 94, adapted to beengaged by sliders 95, 96 and 91, respectively.

The `motor 55 contains a relay having an armature 98 pivoted at 99. Acontact arm |00 is carried by the armature 98 and insulated therefrom byan insulator member |0|. The contact arm |00 is adapted to engage acontact |02 or a contact |03. The armature 98 is operated by relay coils|04, |05, |06 and |01, so that when the coilv |04 is energized more thanthe coil |05, the contact arm |00 is moved into engagement with thecontact |03, and when the coil |05 is energized more than the coil |04the contact arm |06 is moved into engagement with the contact |02.

When the coils |04 and |05 are equally ener- 5 gized, the contact arm|00 assumes a mid position as shown in Figure 2.

The return air thermostat 62 is shown to comprise a mercury switch |08operated by a bimetallic member |09, so that upon an increase in reoturn'air temperature to a predetermined value the mercury switch |08 ismoved to a circuit making position.

Line wires ||0 and lead from some source of power, not shown. A manuallyoperated switch 0 ||2 co-acting with a contact ||3 is connected to ytheline wire ||0. The contact ||3 is connected by wires ||4 and H5 to thefan motor 21 which is in turn connected by'a wire ||6 to theother linewire IH. Therefore, when the switch army 7 H2 is moved into engagementwith the contact H3 the fan motor 24 is-pl'aced in operation. One oftheelectrodes of the mercury switch "l is connected by a wire ||T tothe.junction of the wires v||4 and H5. The other electrode o! the 1 The eldwinding 15 acts in 5 aisance mercury switch |08 is connected by a wire|50 to one end of a primary I 9 of a. step-down transformer having asecondary i 2|. The other end of the primary i I8 is connected by a wirei22 to the junction of wires ||i and H8. By reason of these wiringconnections when the manual switch H2 is closed and the mercury switch|00 is moved to a circuit making position the transformer |20 isenergized.

One end of the secondary |2 I Vof the step-down transformer |20 isconnected by wires |23, |20 and |25, to the contact 95 of the variableresistance 00. contact 95 is connected by a wire |25 to the left handend of the potentiometer coil 88. The other end of the secondary I2I is`connected by wires |21 and |28 to the resistance 90. The slider 91associated with resistance 90 is connected by a wire |29 to the righthand end of the potentiometer coil 89. 'Ihe junction of the wires |20and is.connected by a wire |30 'and a protective resistance to the righthand end of the balancing potentiometer 8|, and the left hand end of the-balancing potentiometer 8| is connected by a protective resistance |3|,a wire ISI, a resistance |32 and a wire |38 to the junction of wire I28and the resistance 90. 'Ihe junction of wires |23 and |26 is connectedby a Wire |30 to the lower end of the coil |00, and likewise thejunction of wires |21 and |28 is connected by a wire to the lower end ofthe coil |05. The upper ends of the coils |00' and |05 are connectedtogether by means of wires |36 and |31, and to the resistance 93 bymeans of wires |38 and |30. The slider 96 co-acting with the resistance93 is connected by a wire |00 to the slider 90 of the dischargetemperature controller 51. 'Ihe left hand end of the potentiometer coil9| is connected by a wire |0| to the junction of the resistance S2, andthe wire |28 and the right hand end of the potentiometer coil 9| isconnected by a Wire |02 to the slider 88 of the space temperaturecontroller 56. The slider 80 associated with the balancing potentiometer8| is connected by a..wire |03 to the junction of the wires |38 and |39.

From the above wiring connections it is seen that the left hand end ofthe secondary I2I, the lower end of the coil |00, the left hand end ofthe potentiometer coil 89, and the right hand end of the balancingpotentiometer coil 8| are connected together. Likewise, the right handend of the secondary I2I and the lower end of the coil |05, the righthand end of the potentiometer coil 89 and the left hand end of thebalancing potentiometer coil 0| The upper ends of the relay coils |00andV |05, and the sliders 88 and `80 are connected together. Therefore,it is seen that the coils |04 and |05, and the potentiometer coils 89and 8|,y are connected in parallel with respect to each other andacrossthe secondary I2| vof the step-down trans# former |20. It isalsoseen that when the slider 88 is moved to its extreme right hand positionthe right hand end of the potentiometer coil 9| is directly connectedtothe, left hand end of the balancing potentiometer 8| and the left handend of the potentiometercoii 0| is connected to the right hand end ofthe balancing potentiometer coil 8|. tremeright position as shown inFigure 2, the system is under thecontrol of,y slider 80 and itspotentiometencoil 08, and that whenthe slider 88 is in its extreme righthand-position the sys- The resistance 82 associated with the v areconnected together..

Therefore, with the slider 00 in its ex-' tem is under the control ofthe slider 00 and its potentiometer coil 0|.

'I'he contact |02 cooperating with the contact arm |00 is connected by awire |05 to one end of the coil |01. The other end of the coil |01 isconnected by a wire |06 to one end of the eld winding 15. The other endof the field winding 15 is connected by wires |01 and |08 to the contact05 of the limit switch. The associated contact 00 is connected by wire|09, resistance |50 and wire |5| to the junction of wires |21 and |28.Thecontact |03 cooperating with the contact arm |00 is connected by awire |52 to one end of the coil 1| 06. The other end of the coil |00 isconnected by a wire |53 to one end of the field Winding 16. The otherend of the eld winding 18 is connected by a wire |50 to the con# tact 81of the other limit switch and the asso- -ciated contact 88 is connected.by a Wire |55 to the junction of wire |5| and the resistance |50. Theleft hand end of the secondary I2I is connected by wirewl, and |51 tothe contact arm |00 and by a wire |58 to one end of the field winding10, the other end thereof being connected to the junction of wires M1and |00.

With the parts in the position shown in the drawings the space or reqmis cold and the unit ventilator is shut down by, reason of the switch||2 being -open. The damper 2| is located in a closed'or fresh airrestricting position by means of the spring 51 and, consequently, thelimit switch 00, 85 is open. The valves 35 and 30 are open to admitheating uid to the radiators 20 and 29, and in response to the heatedcondition of the radiators 28 and 29, slider 80 is in the right handposition with respect 'to its potentiometer coil 9| Due to the fact thatat this time the space or room is cold the slider 88 is at its extremeleft hand position with respect to its potentiometer coil 89. Uponclosing of the manual switch I2 the fan motor 20 is .placed in operationand return air from the space is forced over the radiators 28 and V20.and heated thereby. When the space temperature and, consequently, thereturn air temperature, has risen to agiven value, the mercury switch|08 is tilted to a cir-- cuit making position to supply energy to thestep-down transformer |20. As the temperature in the space begins torise the slider 08 is moved to the right to cause short circuiting orshunting of the coil |05 to increase the energization of the coil |04'and decrease the energization of the coil |05. This causes movement ofthe switch arm |00 into engagement with the contact |03 to complete acircuit from the secondary |2| through 'wires r|50 and |51, contact arm|00, contact |03,wire |52, coil |06, wire |53, iield winding 16, wire|50, contacts' 81 .and 86, and wires |55, |5|and |21, back tothesecondary |2|.- Completion of this circuit causesl energization ofthe-field winding 18 to start movement of the through wires |56 and|50,` field. winding 16,

wire |08, contacts 80 vand-85, wire, |49; resistancey |50, and Wires |5|and |21, back to-the secondary.

I2I. Completion of this circuit causes energization of the fleldwindingmand the field -winding 14 lwill remain energized as long as the contacts84 and 85 are in engagement. Since both the field windings 14 and 16 areenergized in the manner pointed out above, the spring 61 is overcome andthe damper 2| is moved further from the fresh air restricting position.

Movement of the damper 2| from the fresh air restricting position causesright hand movement of the slider 80 with respect to the balancingpotentiometer coil 8|. This causes short circuiting or shunting of thecoil |04 to decrease the energization thereof and increase theenergization of the coil |05, it being remembered that the coil |04 wasenergized more than the coil |05 byreason of the right hand movement ofthe slider 88. When the slider 80 has moved sui.

ciently far to the right, the coils |04 and |05 will become equallyenergized to move the contact arm |00 out of engagement with the contact|03 and into the mid position as shown in Figure 2. This causesde-energization of the eld winding 16, it being remembered that thefield winding 14 still remains energized. When the eld winding 16 isthus de-energlzed the damper 2| is maintained in the newly adjustedposition by the energization of the field winding 14. Since the circuitthrough the field winding 16 hincludes the coil |06 the contact arm |00is moved forcibly in engagement with the contact |03 to prevent relaychatter. i

Upon a decrease in space temperature, the

slider 88 moves toward the left with respect to the potentiometer coil89 to short circuit or shunt the coil |04 to increase the energizationof the coil |05 and decrease the -energization of the coil |04. 'I'hiscauses movement of the contact arm |00 into engagement with the contact|02. Movement of the contact arm I 00 into engagement with the contact.|02 completes a circuit from the secondary |2| through wires |56 and|51, contact arm |00,contact |02, wire |45,coil |01, wire |46, fieldwinding 15, wires |41 and |48, contacts 85 and 84, wire |49, resistance|50 and wires |5| and |21 back to the secondary |2|. Completion of thiscircuit causes energization of the coil 15 `which neutralizes theholding action of the coil 14 to permit the spring 61 to move the damper2| towards a fresh air restricting position. Movement of the damper 2|towards a fresh air restricting position causes left hand movement ofthe slider 80 with respect to its balancing coil 8| and when the slider80 has moved sufliciently far to the left the coils |04 and |05 areagain equally energized to move the contact arm |00 out of engagementwith the contact |02 and tothe mid position as shown in Figure 2. Thiscauses deenergizat-ion of the field winding 15, it being remembered thatthe eld winding 14 remains energized. Therefore, further movement of thedamper 2| towards a fresh air restricting position is stopped. Since thecircuit through the field winding 1 5 includes the coil |01, the contactarm |00 is forcibly held in engagement with the contact |02 to preventrelay chatter. The resistance |50 is included in lthe circuits throughthe field windings 14 and 15 to add resistance in the circuits tocompensate for the decrease in resistance caused by the energization ofthe oppositely-acting field windings 14 vand 15.

Movement of the slider 80 to the extreme left hand position shown inFigure 2 is caused by complete closing movement of the damper 2|. Due-tothe use of the resistance |32 a complete zie-balancing is notestablished by the complete left hand movement of the slider 80, wherebyfurther movement of the damper 2| towards a closed position ispermitted'to insure that the finger 82 will break contact between thecontacts 84 and 85 lof the limit switch to completely shut off thesupply of energyto the eld windings 14 and 15 to prevent undue heatingof the same.

From the above it is seen that I have provided a system for accuratelypositioning a damper in accordance with space temperatures which systemis placed in operation when the space ternperature or return airtemperature rises to a predetermined value.

In some localities it is required to have a minimum amount of fresh airdelivered to the space to be heated, and this amount may vary accordingto the various localities. To cause immediate partial opening of thedamper 2| to provide this minimum amount of fresh air, I have providedin the circuit leading to the controllers 56 and 51 the variableresistance 60. Movement of the slider's 95, 96 and 91 downwardly fromthe position shown in the drawings increases the resistance on the lefthand end of the potentiometer coil 89 and decreases the resistance onthe right hand end of the coil 91. This produces the same effect asmoving the slider 88 to the right with respect to the potentiometer coil89, so that with the slider 88 in the extreme left hand position shownin the drawings, movement of the sliders 95, 96 and 91 downwardly causesopening movement of the damper 2|, the amount of opening movement beingdetermined by the distance through which the sliders 95, 96 and 91 aremoved. Therefore, with the sliders 95, 96 and 91 located in a downwardposition, the damper 2| will be immediately moved to some intermediateposition upon closing of the mercury switch |08.

Referring now to Figure 1, I have diagrammatically shown four positionswhich the cams 42, 43 and 45 may assume. In the position shown whereinline a coincides with the roller 46, the damper 2| is closed and thevalves 34 and 35 are open. Movement of the cams 42, 43 and 45 to theposition Where line b coincides with the roller 46, the damper 2| ispartially open and the valve 35 is about to be closed. Movement of thecams 42,

43 and 45 tothe position Where line c coincides with the roller 46 thedamper 2| is moved to a. further open position and the valve 35 iscompletely closed and the valve 34 is about to be v moved towards aclosed position. Movement of the cams 42, 43 and 45 to a position wherethe line d coincides with the roller 46 causes complete -opening of thedamper 2| and complete closing of the valves 34 and 35. Movement of thecams 42, 43 and 45 in the opposite direction causes exactly the sameoperation but in the reverse order. The cams 42, 43 and 45 are sodesigned, and theV variable resistance is so positioned, that when thethermostat 62 places the control system in operation the damper 2| ismoved to a partially open position corresponding to the line b. Upon anincrease in room temperature so as to move the slider 88 to the rightwith respect to the potentiometer coil 89, the damper 2| is positionedtowards an open position and the valves 34 and 35 are positioned towarda closed position. Preferably, the thermostat 62 is set-so that themercury switch |08 is moved to a circuit making position at 65 and theslider 88 is started in its movement from the left hand position of thepotentiometer 89 at 68I and arrives at the right'hand position withrespect to the potentiometer coil 89 when the space temperature hasrisen to 72". lBy reason of the above settings,

2,1 sacas re-circulated air is heated until the temperature of the airbecomes 65, at which time the damper 2| is moved to a partially openposition to admit a predetermined amount of fresh air to the space. Whenthe temperature of the spacebegins to rise above 68 more fresh air isadmitted and the amount of heat imparted to the air is decreased. Whenthe temperature of the space has risen to 72, 100 per cent fresh air isadmitted to the space and no heat is imparted to the air since at -thistemperature the radiators 28 and 29 are cut off.

With the above operation, and with the room or space temperature at 72,and if the outdoor temperature is cold, raw. air may be delivered intothe space or room, To prevent thisdelivery of raw air into the space orroom, the discharge.

temperature controller 5l is provided and preferably this controller isadjusted so that when the temperature of the discharge air decreasesbelow 65 the slider @d is moved from its right hand position towards itsleft hand position with respect to the potentiometer coil 9i. Since atthis time the slider 66 is at the extreme right end of the potentiometercoil B9, and since the right hand end of the coil 9| is connected to thecoil |65, and since the left hand end of potentiometer coil 6| isconnected to the coil ills, movement of the slider Sil towards the leftshort circuits or shunts the coil |05 to increase the energization ofthecoil itl and decrease the energization of the coil ,IM to cause movementof the contact arm te@ into engagement with the contact m2. |This causesenergization of the field winding l5 to neutralize the action of theileldy winding l@ to allow the spring 6l to move the damper El towardsAa closed position, and to move the valve Sli towards an open position,the amount of movement of the damper, and, consequently, the valve 3Qbeing determinedby the position of the slider Sii. In extremely coldweather the slider Sil may be moved suciently far to the left tocompletely open the valve 3d and partially open the valve 35.

From the above it is seen that I have provided a heating and Ventilating`system which positions a damper and valves according tospace or roomtemperatures, and which also positions the damper and valves inaccordance with discharge temvarious localities of the country.Provision is also made for closing the damper when the unit ventilateris rendered inoperative or in case of power failure. l,

Referring now to Figure-3, a system is provided which gives exactlythesame results as the system disclosed in Figure 2, but the manner foraccomplishing these results is slightly different. This modication usesthe same space temperature controller, the same discharge temperaturecontroller, and the same relay mechanism, these various elements beingconnected together in the manner pointed out above. However, the wire|39 which connects the wire |38 to the resistance 63 in Figure 2connects the wire 38 to a switch arm |62 in Figure 3. Switch arm |62is-adapted to engage a contact |63, which is connected by a wire |39' tothe resistance 93. Therefore, when the switch arm H62 is in engagementwith the contact |63 the operation of this portion of the control systemof Figure 3 is identical with that oiFigure 2. The switch arm |62 isalso adapted to engage a contact itil, which is connected to thejunction o1" wires |24 and |25 so that when the switch arm |62 is inengagement with the contact dell the temperature controllers 56 and elare rendered inoperative to control the proportioning motor and the coill0@ is completely short circui'ted to move the contact arm |00 intoengagement with the contact |02. The switch arm |62 is operated by meansof a relay coil |66 so ihatwhen the relay coil |65 is energized theswitch arm it is moved into engagement with the contact 563 to vplacethe proportioning motor under automatic control, and when the relay coil|66 is (le-energized the switch arm |62 is moved into engagement withthe contact |66 in any suitable manner to prevent automatic operation ofthe proportioning motor and to cause the proportioning motor to assumeone extreme position.

Inthis modification line wires leading from some source of power, notshown, are designated at itil and 366. One end of the primary it@ of thestep-down transformer i2@ having the secondary ii is connected to theline wire |66 and the other end thereof is connected to the line wireits. Therefore, in this modiilcation power is at all times supplied tothe relay. The line wire iilil is also connected by a. wire Il@ to aswitch arm' lll, co-acting with a contact H2. Contact l isconnected bywires H3 and i'lfi to the ian motor 2li, and the fan motor 2l is in turnconnected by wires H5 and il@ to the other line wire 66S. The junctionof Wires H3 and lid is connected by a wire i'l'l to one of theelectrodes of the mercury switch M36. Theother electrode of the switchtilt is connected by a wire H6 to one end of the relay coil i66. Theother end of relay coil M36 is connected by a wire ile to the junctionof wires H5 and H6. Therefore, when the switch arm ill is moved intoengagement with the contact H2 the fan motor 2l is placed in operation,and when the room temperature, or return air temperature, reaches apredetermined value, say 65 as in the previous modiiication, the mercuryswitch Eil@ is moved to a circuit making position to cause energizationof the relay coil |66. This moves the switch arm ieg into engagementwith the contact i163 to place the unit ventilator under automaticcontrol and to permit movement of the proportioning motor out of itsextreme position. f

The proportioning motor in the modicatlon shown in Figure 3 is differentfrom that disclosed in Figure 2, and may be of the type disclosed inapplication Serial No. 673,236, flied by Lewis L. Cunningham, on May 27,1933. For purposes of illustration, this motor is shown to compriserotors |63 and 462 operating through the reduction gear train i2, andthegear lli for operating the shaft liti. The rotors iti and |62 areoperated by iield windings |83 and |36, respectively, so that uponenergization of the field windingid the damper is moved towards a closedor fresh air restricting position, and upon energizationof the fieldwinding l8r?, the damper 2i is moved towards an open or return airrestricting position. The manner in which the slider t@ is moved withrespect to the potentiometer balancing-coil 3i, and in which the limitswitches 6ft, 65 86' and The contact |03 cooperating with the contactarm is connected by a wire |85 to one end of the coil |06, the other endof which is connected by a wire |81 to the contact 86 of the right handlimit switch. In a like manner the contact |02 cooperating with thecontact arm |00 connected by a wire |86 to one end of the coil |01, theother end of which is in turn connected by a wireA |88 to the contact 84of the left hand limit switch. Contact 81 is connected by a wire |90 toone end of the field winding 84, and the contact 85 is connected by awire |9| to one end of the field winding 83. The other ends of the eldwindings |83 and |84 are connected together and by a wire |92 to thejunction of the wires |21 and |28. The contact arm |00 is connected bywires |93 and |23 to the secondary |2|.

Assume that the space temperature has risen sufficiently high to causemovement of the switch arm |62 into engagement with the contact |63 inthe manner pointed out above, an increase in space temperature causingmovement of the slider 88 to the right with respect to its potentiometercoil 89 increases the energization of the coil |04 and decreases theenergization of the coil |05. This causes movement of the switch arm |00into engagement with the contact |03 to complete a circuit from thesecondary |2| through wires |23 and |93, contact arm |00, contact 03,wire |85, coil |06, wire |81, contacts 86 and 81, wire |90, fieldwinding |84 and wires |92 and |21 back to the secondary |2|. 'Ihiscauses energization of the field winding |84 to move the damper 2|towards an open position. When the damper has moved suiciently fartowards an open position the slider 80 and the balancing potentiometercoil 8| cause re-balancing of the coils |04 and |05 to move the contactarm |00 away from the contact |03 and into the mid position shown in thedrawings to stop movement of the damper. Likewise upon a decrease inspace temperaturev to move the slider 88 towards the left with respectto its potentiometer coil 89 the coil is energizedV more than the coil|04 to move the contact armA |05 into engagement with the contact |02.This causes completion of a circuit from the secondary |2| through wires|23 and |93, contact arm |00, contact |02, wire |86, coil |01, wire |88,contacts 84 and 85, wire |9|, eld winding |83 and wires |92 and |21 backto the secondary |2|. Completion of this circuit causes'energization ofthe field winding |83 to move the damper 2| towards a closed or freshair restricting position, the amount of movement l being determined bythe slider 80 and the potentiometer coil 8|. From the above, it is seenthat the dampe1L2| is positioned according to space temperatures as inprevious modification.

Movement of the sliders 95, 96 and 91 downwardly with respect to theirresistances 92, 93 and 94 has the same effect as in the previousmodification, so that when the switch arm |62 is moved into engagementwith the contact |63 under the command of the return air thermostat 62,the damper 2| is moved to a minimum fresh air position, -furthermovementof the damper being controlled by the movement of the slider 88 withrespectto the potentiometer coil 89.

From the'above it is seen that I have pro-v vided a control system foran air conditioning unit which may be of the plenary type but whichvfinds particular utility in connection with a unit ditioned, and thatupon increases in space temperature the amount of fresh air delivered tothe space is increased and the amount of heat delivered to the space isdecreased. Provision is made whereby the amount of fresh air initiallydelivered to the space may be varied and provision is also made forcontrolling the damper and the valves, whereby raw air is prevented frombeing admitted to the space.

Although I have shown two exemplifcations of my invention, it isapparent that modifications thereof may become apparent to those skilledin the art, and, therefore, I intend that my invention shall be limitedonly by the scope of theappended' claims and the prior art.

I claim as my invention:

1. In a conditioning unit of the class described for dischargingconditioned air to a space, damper means in said unit for controllingthe supply of air to said unit, means in said unit for altering thetemperature of .the air discharged into the space, a motor in control ofsaid damper means and said temperature altering means, a relaycomprising series connected coils in control of said motor, said seriesconnected coils being connected across a source of electrical energy, aspace temperature responsive adjustable potentiometer, a discharge yairtemperature responsive adjustable potentiometer, connections betweenopposite ends of the series connected coils and opposite ends of theresistance of the first potentiometer, connections between one end ofthe resistances of each potentiometer, connections between the slider ofthe first potentiometer and the other end of the second potentiometer,and connections between the slider of the second potentiometer and thejunction of the series connected coils, whereby when the discharge airtemperature responsive potentiometer is in one extreme position thespace temperature responsive potentiometer is in control of said motorand when the space temperature responsive potentiometer is in oneextreme position the discharge air temperature responsive potentiometeris in control of said motor.

2. In an air conditioning device for conditioning a space, damper meansfor controlling the supply of fresh air and return air into said device,heat exchanger means for changing the temperature of the air dischargedinto the space, valve means for controlling4 the temperature changingeiect of the heat exchanger means, an electric motor, operating meansoperated by 'the electric motor for operating the damper means and thevalve means in a predetermined sequence, means for biasing saidoperating means to a position to open the valve means wide and toprevent the supply of fresh air, control means for controlling theoperation of the electric motor including means responsive to spacetemperature to position said damper means and said valve means inaccordance with variations in space temperature, means included in saidcontrol means for preventing movement of the damper means to thevposition which prevents the supply of fresh air, and means forinterrupting the supply of energy to the electric motor whereby thebiasing means moves the damper means to the extreme biasedposi tion.

3. In an airconditioning device for conditioning a space, damper meansfor controlling the lsupply of fresh air and return air 'into saiddevia'heat exchanger means forchanging the temperature of the airdischarged into the space,

vvalve means for controlling the temperature changing'eiect of the heatexchanger means, an electric motor, operating means operated by theelectric' motor for operating the damper means` and the valve means in apredetermined sequence, control means for controlling the op*- erationof the electric motor, including means responsive to space temperatureto increase the supply of fresh air and close the valve means as thespace temperature increases, means responsive to discharge temperatureto decrease the supply of fresh air and open the valve means as thedischarge temperature decreases, and means included in said controlmeans for preventing movement of the damper means to a fresh airpreventing position regardless of the controlling action of thetemperature responsive means.

4. In an air conditioning device for conditioning a space, damper meansfor controlling the supply of fresh air and return air into said device,heat exchanger means for changing the temperature of the air dischargedinto the space, valve means for controlling the temperature changingeffect of the heat vexchanger means, an electric motor, operatingmeansvoperated by the electric motor for operating the damper means andthe valve means in a predetermined sequence, means for biasing saidoperating means to a position to open the valve means wide and toprevent the supply Vof fresh air, control means for controlling theoperation of the electric motor including means responsive to spacetemperature to position said damper means and said valve meansinaccordance with variations in space temperature, means included insaid control means for preventing movement of the damper means to theposition which prevents the v supply of fresh air, means forinterrupting the supply of energy to the elect'ric motor whereby thebiasing means moves the damper means to the extreme biased position, andmeans responsive to space temperature for controlling said lastmentioned means.

5. In a conditioning unit of the class described for dischargingconditioned air to a space, damper means in said unit for controllingthe :dow of air through said unit, a motor in control of said' dampermeans, a' relay comprising series connected coils in control of saidmotor, said series connected coils being connected across a source ofelectrical energy, a space temperature responsive adjustablepotentiometer, a discharge air temperature responsive adjustablepotentiometer, connections between opposite ends of the series connectedcoils and opposite ends of the resistance of the first potentiometer,connections between one end of the resistances of each potentiometer,connections between the slider of the first lpotentiometer and the otherend of the second potentiometer, and connections between the slider ofthe second potentiometer and the junction of the series connected coils,whereby when the discharge air temperatnre responsive potentiometer isin one extreme position the space temperature responsive potentiometeris in control of said motor and when the space temperature responsivepotentiometer is in one extreme position the discharge air temperatureresponsive potentiometer is in control of said' motor.

6. In an air conditioning system, in combination, means for supplyingfresh air to a space to be conditioned, damper means movable betweenclosed and open positions for controlling the fresh air supply, electricmotor means for moving said damper means to various positions, a controlcircuit for said electric motor means for controlling the operationthereof, a first temperature responsive electric current controllingmeans responsive to a temperature condition which is affected by theposition of the fresh air damper means and being connected in saidcontrol cir'- cuit in a manner to position said electric motor means andhence said damper means to maintain said temperature conditionsubstantially constant, a second temperature responsive electric currentV controlling means responsive to another temperature condition andbeing connected in said motor control circuit with said iirsttemperature responsive electric current controlling means in a manner torender said first temperature responsive current controlling meanssubstantially ineffective to position said electric motor means andtoposition substantially independently said electric motor means and hencesaid damper means whenever the temperature condition to which saidsecond temperature responsive electric current controlling meansresponds varies to a predetermined value, means included in said controlcircuit for normally preventing either of said temperature responsiveelectric current controlling means from completely closing said fresh Yair damper means, and meansfor completely closing said fresh air dampermeans regardless of the controlling action of the temperature responsiveelectric current controlling means.

'7. In combination, an air conditioning unit having temperaturechanging'means and means for supplying fresh air to a space to beconditioned, damper means movable between open and closed positions forcontrolling the fresh air supl ply, motor means for moving Said dampermeans to various positions, means including first temfective to positionsaid motor means and to position substantially independently said motormeans and hence, said damper means whenever the second temperaturecondition varies to a predetermined value, means for normally preventingeither of said temperature responsive means from completely closing saidfresh air damper means,A

and means operative as an incident to shutting downof a portion of theair conditioning unit for completely closing the fresh air damper means.

8. In combination, an air conditioning `unit having temperature changingmeans, fresh air supplying means and fan means for circulating airthrough the unit to a space to be conditioned, damper means movablebetween open and closed positions for controlling the fresh air supply,motor means for moving said damper means to various positions, meansincluding rst temperature responsive means responsive to va temperaturecondition which is affected by the position of the fresh air damper forpositioning said motor means and hence said dampermeans to maintain saidtemperature responsive means substantially inefmeans for normallypreventing either of said` temperature responsive means from completelyclosing said fresh air damper means, and means operative upon stoppingof the fan means for completely closing said fresh air damper means.

9. In an air conditioning system, in combination, damper means forcontrolling the supply of fresh air to a space to be conditioned,electric motor means for operating said means, a three A wire controlcircuit for 4said motor means, said three wire control circuit includinga common wire, a first control wire which is adapted in cooperation withsaid common wire to cause said electric motor means to operate in onedirection and a second control wire which is adapted in cooperation withsaid common wire to cause said motor meansto operate in the oppositedirection, thermostatic electric current controlling means responsive toa temperature iniluenced by the damper position, said last mentionedmeans including a movable member connected to said common Wire and meanscontacted by said movable member and adapted to place said common andcontrol wires in cooperation respectively, said thermostatic electriccurrent .controlling means acting normally to cause positioning of said'damper means in a manner to maintain said temperature conditionsubstantially constant, a second thermostatic electric current'controlling means responsive to another temperature condition, saidsecond thermostatic current controlling means including means connectedto said common wire and one of said control Wires for rendering saidflrst current controlling means inef-` direction when the temperature atsaid second thermostatic electric current controlling means is at onevalue, while placing said first current controlling means in control ofsaid motor means when the temperature at said second thermostaticelectric current controlling means is at another value.

10. In an air conditioning system, in combination, electrically operatedfan means for supply- 'ing fresh air to a space to be conditioned, an

electric circuit for the fan means, damper means movable between openand closed positions for controlling the fresh air supply, electricmotor means for moving said damper means to various positions, means forsupplying power to the elec- .tric motor means from the electric circuitfor the fan means, means for biasing the damper means toward a closedposition, control means including first temperature responsive meansresponsive to a temperature condition which is affected by the positionof the fresh air damper for positioning said electric motor means andhence said damper means to maintain said temperature conditionsubstantially constant, said control means also including a secondtemperature responsive means responsive to another temperature conditionto render said first temperature responsive control means substantiallyineiective to position said electric motor means and to positionsubstantially independently said electric motor means and 1 hence saiddamper means whenever the second temperature condition varies to apredetermined value, means for normally preventing either of saidtemperature responsive means from completely closing said fresh airdamper means, and

means for interrupting the electric circuit for the fan means to stopthe fan means and to stop the supply of power to the electric motormeans whereby the biasing means moves the damper means to the completeclosed position.

JNO. T. MIDYETTE, Jn.

